Exception in ConsumeAsync: Could not find a part of the path '/Users/******/yur/p1/obj/xcode/AppDelegate.h'

this: https://github.com/dotnet/xcsync/blob/7e95dff4ec8a211a26f9e6b69bcbb20c26b51950/src/xcsync/Commands/BaseCommand.cs#L204

isn't doing what it is supposed to when executing the generate command for the _very_ first time. It results in:

> ./xcsync generate -p /Users/`******`/yur/p1/p1.csproj -tfm net9.0-ios -f -v Detailed
xcSync v42.42.42.42, (c) Microsoft Corporation. All rights reserved.
[16:04:58 INF xcsync (1)] Using Xcode from /Applications/Xcode_15.4.0.app.
[16:04:59 INF xcsync (1)] Using the `dotnet` located at .
[16:04:59 INF xcsync (1)] Generating files from project '/Users/`******`/yur/p1/p1.csproj' to target '/Users/`******`/yur/p1/obj/xcode'
[16:04:59 DBG xcsync (1)] Generating Xcode project files...
Executing: dotnet msbuild /Users/`******`/yur/p1/p1.csproj -getProperty:UseMaui,OutputType -getResultOutputFile:/var/folders/qc/z5px468n56j2pnk6ltpctn5c0000gn/T/tmp1LATWI.tmp
[16:05:04 DBG xcsync (9)] Generated Xcode header and implementation files
[16:05:04 FTL xcsync (18)] Exception in ConsumeAsync: Could not find a part of the path '/Users/******/yur/p1/obj/xcode/AppDelegate.h'.
Executing: dotnet msbuild /Users/`******`/yur/p1/p1.csproj -getItem:Compile,None -property:TargetFramework=ios -getResultOutputFile:/var/folders/qc/z5px468n56j2pnk6ltpctn5c0000gn/T/tmpZztvRo.tmp
[16:05:04 FTL xcsync (18)] Exception in ConsumeAsync: Could not find a part of the path '/Users/`******`/yur/p1/obj/xcode/AppDelegate.m'.
Executing: dotnet msbuild /Users/`******`/yur/p1/p1.csproj -getItem:BundleResource -property:TargetFramework=net9.0-ios -getResultOutputFile:/var/folders/qc/z5px468n56j2pnk6ltpctn5c0000gn/T/tmptoprQU.tmp
Executing: dotnet msbuild /Users/`******`/yur/p1/p1.csproj -getProperty:SupportedOSPlatformVersion -property:TargetFramework=net9.0-ios -getResultOutputFile:/var/folders/qc/z5px468n56j2pnk6ltpctn5c0000gn/T/tmpDDP5Fd.tmp
[16:05:07 INF xcsync (9)] Generated Xcode project at '/Users/`******`/yur/p1/obj/xcode'
[16:05:07 DBG xcsync (18)] Synchronization complete.

in the above stack trace, we only see issues with the AppDelegate files. Why not any of the static ones like Info.plist?
because we ensure the directory is created for apple-specific files: https://github.com/dotnet/xcsync/blob/7e95dff4ec8a211a26f9e6b69bcbb20c26b51950/src/xcsync/SyncContext.cs#L173

also, I don't think we should be manually handling the `DirectorySeparatorChar` in: https://github.com/dotnet/xcsync/blob/7e95dff4ec8a211a26f9e6b69bcbb20c26b51950/src/xcsync/Commands/BaseCommand.cs#L52

I believe this might be contributing to the issue here. Regardless, the logic here should be more consistent